The invention relates to a conference switching system, and more specifically, a PCM switching system, in which a sum signal is formed for each participant in the conference from speech samples of the relevant participant, and a speech intensity is determined for each participant on the basis of which each share of the speech sample in the sum signal is determined.
DE-PS 33 29 779 to which U.S. Pat. No. 4,607,362 corresponds, discloses a method of establishing conference connections in a PCM private branch exchange, in which in a conference arrangement during a pulse frame the compressed codewords received from participants are linearized and buffered and in which, prior to transmission to the participant, during a next pulse frame a final sum codeword is formed and delineatized to the compressed codeword. Meanwhile, during the pulse frame, the speech intensities of the individual participants are measured and the weighting factors are adapted in dependence on these speech intensities.
For this purpose, the speech samples of each participant in the conference are applied to a measuring arrangement which measures the speech intensities of the individual participants. A participant whose measured speech intensity exceeds a predeterminable threshold is graded as actively speaking. This predeterminable threshold for each participant may be individually adapted in accordance with each participant's speech intensity measured during his previous conversation.
Many participants do not always feel the acoustic impression of reproduction according to that method to be "natural".